docs: def _download_py3(link, path, __hdr__):
      """Download a file from a link in Python 3."""
      try:
          req = urllib.request.Request(link, headers=__hdr__)
          u = urllib.request.urlopen(req)
      except Exception as e:
          raise Exception(' Download failed with the error:\n{}'.format(e))
  
      with open(path, 'wb') as outf:
          for l in u:
              outf.write(l)
      u.close()